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Hi, guys. =97 said the shy newcomer.
I've started reading The D Programming Language just yesterday and I'm
making my first attempts to dig into D now. I must say I'm loving the
language beyond recognition. I never thought there was a language out there
that had everything I ever wanted in C++ (I even considered developing my
own language before knowing D!).
Right now I'm wondering how's the best way to create a dynamic array object
which will only accept "unique" elements (i.e., elements !=3D from the
existing elements in the array).
I wanted a class that kept all the functionality of an array (e.g. being th=
e
right range types so that they can be passed to std.format.formatValue and
trigger the right specialization) for maximum integration with the standard
library. I thought about writing a class template privately containing an
array and redirecting everything but the assignment/insertion operations to
it. All ways of placing an object that was already there should throw an
exception, but everything else should work the same.
Doing it this way is a lot of work for a simple thing, so some sort of
internal alert in me tell me I might just be "doing-it-wrong". I want to
know what your ideas are.
I want some way to achieve this sort of thing:
import myproject.helpers.UniqueArray;
void main()
{
auto a0 =3D [1, 2, 3];
// I'm not yet sure how to go about the constructor, since:
auto a1 =3D UniqueArray!(int)(a0[1 .. $]); // error: should not be able=
to
internally hold reference to
// a raw array since this coul=
d
be used to break the "unique
// elements" contract promise
of UniqueArray
// copy of elements can be
considered, but I'd rather
// have clients copy the array
themselves so that they
// know it is happening
auto a2 =3D UniqueArray!(int)(a0[1 .. $].dup); // should be fine if D h=
ad
some sort of non-const
// rvalue reference
support, but I think it does not;
// am I wrong?
auto a3 =3D UniqueArray!(int)(a0[1 .. $].idup); // semantically pleasin=
g
at first sight, but
// suboptimal: the
constructor would have to copy
// the passed array again
to get rid of immutability
auto a4 =3D bestOptionOutOf(a1, a2, a3); // (:
a4[1 .. $] =3D [3, 4, 5]; // ok: would first construct a UniqueArray ou=
t
of the rvalue (thus ensuring
// "uniqueness" of elements) and then would wor=
k
like a usual slice
// assignment
a4 ~=3D 5; // throws exception: 5 is already in the array!
a4 ~=3D 6; // ok: 6 is not there
writeln(a4); // ok, output: [2, 3, 4, 5, 6]
// could just implement UniqueArray.toString() for this to
work, but making UniqueArray
// properly model the ranges an array models solves this
problem and others at the same
// time
auto a5 =3D a4.dup; // all properties of an array, such as dup here,
should hold and overall
// the object should behave as one would expect from
an array
int[] a6 =3D a5; // error: obviously shouldn't work since a6 could then=
be
used to break the
// UniqueArray contract
}
What do you think?
--=20
Atenciosamente / Sincerely,
Guilherme ("n2liquid") Vieira
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Hi, guys.=A0<span class=3D"Apple-style-span" style=3D"font-family: sans-ser=
if; font-size: 12px; line-height: 18px; -webkit-border-horizontal-spacing: =
2px; -webkit-border-vertical-spacing: 2px; ">=97 said the shy newcomer.</sp=
an><div>
<font class=3D"Apple-style-span" face=3D"sans-serif"><span class=3D"Apple-s=
tyle-span" style=3D"font-size: 12px; line-height: 18px; -webkit-border-hori=
zontal-spacing: 2px; -webkit-border-vertical-spacing: 2px;"><br></span></fo=
nt></div>
<div><font class=3D"Apple-style-span" face=3D"sans-serif"><span class=3D"Ap=
ple-style-span" style=3D"font-size: 12px; line-height: 18px; -webkit-border=
-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px;">I&#39;ve s=
tarted reading The D Programming Language just yesterday and I&#39;m making=
my first attempts to dig into D now. I must say I&#39;m loving the languag=
e beyond recognition. I never thought there was a language out there that h=
ad everything I ever wanted in C++ (I even considered developing my own lan=
guage before knowing D!).</span></font></div>
<div><font class=3D"Apple-style-span" face=3D"sans-serif"><span class=3D"Ap=
ple-style-span" style=3D"font-size: 12px; line-height: 18px; -webkit-border=
-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px;"><br></span=

ple-style-span" style=3D"font-size: 12px; line-height: 18px; -webkit-border=
-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px;">I wanted a=
class that kept all the functionality of an array (e.g. being the right ra=
nge types so that they can be passed to std.format.formatValue and trigger =
the right specialization) for maximum integration with the standard library=
. I thought about writing a class template privately containing an array an=
d redirecting everything but the assignment/insertion operations to it. All=
ways of placing an object that was already there should throw an exception=
, but everything else should work the same.</span></font></div>
<div><font class=3D"Apple-style-span" face=3D"sans-serif"><span class=3D"Ap=
ple-style-span" style=3D"font-size: 12px; line-height: 18px; -webkit-border=
-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px;"><br></span=

Hi, guys. — said the shy newcomer.
I've started reading The D Programming Language just yesterday and I'm
making my first attempts to dig into D now. I must say I'm loving the
language beyond recognition. I never thought there was a language out
there that had everything I ever wanted in C++ (I even considered
developing my own language before knowing D!).
Right now I'm wondering how's the best way to create a dynamic array
object which will only accept "unique" elements (i.e., elements !=
from the existing elements in the array).
I wanted a class that kept all the functionality of an array (e.g.
being the right range types so that they can be passed to
std.format.formatValue and trigger the right specialization) for
maximum integration with the standard library. I thought about writing
a class template privately containing an array and redirecting
everything but the assignment/insertion operations to it. All ways of
placing an object that was already there should throw an exception,
but everything else should work the same.
Doing it this way is a lot of work for a simple thing, so some sort of
internal alert in me tell me I might just be "doing-it-wrong". I want
to know what your ideas are.
I want some way to achieve this sort of thing:
import myproject.helpers.UniqueArray;
void main()
{
auto a0 = [1, 2, 3];
// I'm not yet sure how to go about the constructor, since:
auto a1 = UniqueArray!(int)(a0[1 .. $]); // error: should not
be able to internally hold reference to

I suspect the best would be to copy whatever got passed to constructor,
since to provide such contracts UniqueArray needs to own data. Also you
could use fancy homogeneous variadic function for ctor:
this(T[] args...){
_payload = args.dup;//assume member _payload holds internal array
}
Then
auto a = UniqueArray!(int)(1,2,3,4);//fills array with elements [1,2,3,4]
auto a = UniqueArray!(int)([5,6,7]); //works with the same signature

// a raw array since
this could be used to break the "unique
// elements" contract
promise of UniqueArray
// copy of elements
can be considered, but I'd rather
// have clients copy
the array themselves so that they
// know it is happening
auto a2 = UniqueArray!(int)(a0[1 .. $].dup); // should be fine
if D had some sort of non-const
// rvalue
reference support, but I think it does not;
// am I wrong?
auto a3 = UniqueArray!(int)(a0[1 .. $].idup); // semantically
pleasing at first sight, but
// suboptimal:
the constructor would have to copy
// the passed
array again to get rid of immutability
auto a4 = bestOptionOutOf(a1, a2, a3); // (:
a4[1 .. $] = [3, 4, 5]; // ok: would first construct a
UniqueArray out of the rvalue (thus ensuring
// "uniqueness" of elements) and then
would work like a usual slice
// assignment
a4 ~= 5; // throws exception: 5 is already in the array!
a4 ~= 6; // ok: 6 is not there
writeln(a4); // ok, output: [2, 3, 4, 5, 6]
// could just implement UniqueArray.toString()
for this to work, but making UniqueArray
// properly model the ranges an array models
solves this problem and others at the same
// time
auto a5 = a4.dup; // all properties of an array, such as dup
here, should hold and overall
// the object should behave as one would
expect from an array
int[] a6 = a5; // error: obviously shouldn't work since a6
could then be used to break the
// UniqueArray contract
}
What do you think?
--
Atenciosamente / Sincerely,
Guilherme ("n2liquid") Vieira

I've done something like this before using associative arrays. I would
rely on the fact that the keys have to be unique to produce my unique
array. So, in this case, any value you want to store you would save
like this:
array[value] = 1;
Regardless of whether or not the value already exists, this will work
and ensure uniqueness of the keys. To determine if a value is already
part of the array, you can check for the key like this:
if (value in array)
You can later get the values like this:
values = array.keys;
Not sure if this will do everything you want, but it seems to be cleaner
than having to ensure an array is unique after every insertion.
Casey